color faces with wrong normals
There are several things you could do to make finding flipped normals easier.


Turn on Backface Culling. In edit mode press N then scroll down to the Shading section. Check the box for Backface Culling. That will make all the backs of the faces clear, so if one is backwards it will be completely transparent.
Turn on the display of normals. In edit mode press N then scroll down to the Mesh Display section. Check the box for Display face normals. That will show little lines pointing out from each face, if a face is backwards then the line will point in.  

  
You can make a simple cycles material to show the backwards faces. The two Diffuse shaders are used to get the red and white colors. The Geometry node has a backfacing socket, that plugged in to the mix shader makes the difference between the correct faces and the backwards faces.

This will display flipped faces as red while in material view, but if your graphics card does not support GLSL you will have to be in Rendered view.